Diving computers are commonly used by divers to monitor key parameters, such as remaining air, present depth, compass (direction), etc. This has changed the way dives are planned. Before the diving computer was introduced, each dive was carefully planned and the diving schedule was decided in advance. With a diving computer, divers rely on it and usually turn to the surface when there is a certain air level in the tank, such as ⅓ remaining air (100 bar air pressure).
In more advanced prior art systems, it is possible to optimize the diving time by programming the monitoring unit to measure the air consumption for the diver and thereafter calculate the remaining time. However, this requires the diver to be observant regarding the remaining time provided from the monitoring unit instead of the usual key parameter, i.e. remaining air.
In the eighties, it was a natural part of diving to tie the divers together with a rope, a so called “buddy line”, but this is nowadays more seldom used. Today, divers try to keep their dive partners under observation but accidents regularly happen and a dive partner is lost.
In a publication by Vann R D, Lang M A, eds. with the title “Recreational Diving Fatalities”. Proceedings of the Divers Alert Network 2010 April 8-10 Workshop. Durham, N.C.: Divers Alert Network, 2011. ISBN #978-0-615-54812-8, which is incorporated by reference, it is stated on page 41 that “Every year, approximately 125 divers die in North America, Europe and Asia (Denoble, Vann 2009).”
Furthermore, a staggering number of 947 recreational open-circuit scuba diving deaths from 1992 to 2003 was presented in the publication. The major cause of death is drowning (70%) but the reasons behind the deaths are more difficult to determine. On page 45 in the publication, last paragraph, it is stated “Although triggers were identified in only one-third of cases (346 of 947), the most common triggers were identified as insufficient gas (41 percent), entrapment (20 percent) and equipment problems (15 percent). Similarly, disabling agents were identified in only one-third of cases (332 of 947); however, emergency ascent (55 percent), insufficient gas (27 percent), and buoyancy trouble (13 percent) were the most common disabling agents and, together, accounted for 95 percent of the 332 deaths.”
From these observations, it is clear that there is not only important to monitor your own key parameters when diving, but also monitor your dive partner's key parameters to prevent any of the above mentioned triggers or disabling agents.
A system providing a solution to this need has been presented by a company called Liquivision, and the system (named Lynx) operates using ultrasonic waves. The system is briefly described in connection with FIG. 1 and transmitters, either on a diver 1, on a boat 2 or stand alone on the bottom 3, creates an underwater network based on ultrasonic waves. Specially designed dive computers carried by the divers can receive the transmitted ultrasonic waves and obtain information from the transmitters.
A drawback with the system presented by Liquivision is that the information transmitted within the network is one way, and communication between divers cannot be achieved.
There is also a desire to provide improved positioning of divers. While vehicles and persons moving about on land or in the air may use GPS or similar satellite based systems, this is not possible for divers due to the attenuation of radiowaves in water. There is thus a need for an improved method of positioning a diver under water.